JP2000306869A - Abrasive and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To vary polishing rate for a metallic film, barrier film and insulating film arbitrarily by using silica, having a predetermined specific surface area as abrasive grains and mixing oxalic acid, an oxidizing agent and water in properly adjusted amounts with the silica. SOLUTION: As abrasive grains, silica is used whose specific surface area is about 20 m2/g or larger and smaller than about 80 m2/g. By varying the concentration of silica and the concentrations of oxalic acid and an oxidizing agent of other components, the polishing speed is adjusted arbitrarily. The remaining component is water. The concentration of silica is preferably within the range of about 0.1-20 wt.%. Furthermore, the concentration of oxalic acid is preferably within the range of about 0-1 wt.%. When polishing a metallic film 4, the concentration of oxalic acid is set to a larger value, and for reducing the polishing speed for the film 4, the concentration of oxalic acid is set to a smaller value. Still further, the concentration of the oxidizing agent is preferably within the range of about 0-10 wt.%. When polishing the film 4, the concentration of the oxidizing agent is set to a highish value, and to reduce the polishing speed for the film 4, the concentration of the oxidizing agent is set to a lowish value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel polishing agent and a polishing method using the same. More specifically, the metal film or the metal film and the barrier film can be polished at a practical polishing rate while keeping the dissolution characteristics of the metal film low, and the polishing rate can be arbitrarily varied by changing the ratio of the components. The present invention provides an abrasive which can be used, and a polishing method which can accurately manufacture semiconductor devices using the above-mentioned abrasive.

[0002]

2. Description of the Related Art Along with the high integration of semiconductor devices, wiring technology has been increasingly miniaturized and multilayered. Then, with the progress of the multilayering of the wiring technology, the step on the surface of the semiconductor substrate becomes large, and furthermore, there is a problem that the processing accuracy and reliability of the wiring formed thereon are reduced, and miniaturization is hindered.

In order to solve the above-mentioned problems caused by the multi-layer structure, a technique has been developed in which a layer on which a wiring pattern, an electrode, etc. (hereinafter, referred to as a wiring, etc.) is formed is flattened, and further a wiring, etc. is formed thereon. ing. That is, as shown in FIG.
(A) An insulating film 2 having a concave portion A for metal wiring is formed on the surface of a semiconductor substrate 1, and (b) a metal film 4 is formed thereon so as to fill the concave portion via a barrier film 3. (C)
In this method, a metal film other than the metal film filling the concave portion and the barrier film are removed by polishing to form a flat surface of the insulating film and the metal film filling the concave portion.

In the above technique, the barrier film has a function of preventing aluminum or copper used as a metal film from diffusing into the insulating film and improving the adhesion of the metal film to the surface of the semiconductor substrate. In general, titanium nitride, tantalum nitride, or the like is used.

The above-mentioned polishing method employs a method of using both mechanical polishing and a chemical reaction which promotes the polishing in order to realize high polishing performance. This method is called a chemical mechanical polishing (hereinafter, abbreviated as CMP) method, and various compositions of polishing agents to be used according to a polishing target such as a metal film, an insulating film, and a barrier film have been proposed. The general composition of the above-mentioned abrasive is composed of abrasive grains and a chemical.

In the above-mentioned abrasive, if the polishing rate ratio (hereinafter also referred to as selection ratio) of each film can be set to 1, it is possible to uniformly polish all the films using such an abrasive. .

However, there is no ideal polishing agent having the above-mentioned selection ratio of 1, and usually, an polishing agent having a high selection ratio of the metal film is used, and the metal film is polished using the barrier film as a stop layer. Thus, a method is employed in which the barrier film is polished in place of a polishing agent having a low selectivity between the metal film and the barrier film. Also in this case, there is no abrasive having a practical polishing rate and a selectivity close to 1 and some unevenness is caused by preferentially polishing either the metal film or the barrier film. For this reason, in many cases, a method is used in which after the insulating film is polished, the polishing is performed using another polishing agent having a different selection ratio.

[0008]

However, the above-mentioned polishing method comprises polishing a metal film, polishing a barrier film and a metal film,
By the time all polishing steps for polishing the metal film, the barrier film, and the insulating film are completed, several types of polishing agents having different selectivity and changing the selection ratio of polishing abrasives and acids must be used.

[0009] Therefore, there are problems that a plurality of polishing apparatuses are required, and that a large amount of time and labor is required for replacement and preparation of abrasives when processing with one polishing apparatus. there were.

In the conventional polishing agent, even if the selectivity is adjusted, in the actual polishing step, the metal to be polished is dissolved by the agent, and the recesses on the surface of the insulating film to be left as wiring are filled. Metal becomes thinner (hereinafter referred to as
This phenomenon is called dishing). When this dishing occurs, a wiring failure easily occurs. Therefore, it is necessary to suppress the occurrence of dishing as much as possible. In addition, even though no apparent dishing is observed, a thin corrosion layer (oxide film) is often formed on the surface of the metal film.

As described above, in the conventional polishing method, the necessity of using a plurality of abrasives necessitates the use of a plurality of polishing apparatuses and the labor and time for exchanging the abrasives. At present, the problem of dishing caused by the above-mentioned chemicals has not been sufficiently solved.

[0012]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems. As a result, silica having a specific specific surface area is used as abrasive grains, and a polishing agent comprising oxalic acid, an oxidizing agent, and water is appropriately adjusted only for the amount of the components, whereby the metal film, the barrier film, and the insulating film are formed. Since the polishing rate can be arbitrarily changed, it has been found that a single polishing machine can continuously polish a semiconductor substrate and a flatter semiconductor substrate surface can be formed. Further, the above-mentioned polishing agent was found to be excellent also in the dissolution resistance (dishing) of the metal film, and completed the present invention.

That is, according to the present invention, the specific surface area (hereinafter, simply referred to as specific surface area) measured by the BET method is 20 m ² /
g to less than 80 m ² / g of silica, 0.1 to 20% by weight, oxalic acid at 0 to 1% by weight, and oxidizing agent at 0 to 10% by weight.
A polishing agent that can arbitrarily change the polishing rate of a metal film, a barrier film, and an insulating film, wherein the polishing agent contains water, with the balance being water.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an abrasive and a polishing method according to the present invention will be described in detail.

According to the present invention, the abrasive has a specific surface area of 20 m ^2.
/ G or more and less than 80 m ² / g, preferably 25
The use of silica at あ る 80 m ² / g is important in order to arbitrarily adjust the selectivity by changing its own concentration, the concentrations of the other components oxalic acid and oxidizing agent. For example, when silica having an upper limit of the specific surface area of 80 m ² / g or more is used, the polishing rate of the barrier film and the insulating film is not sufficiently increased, and the metal film and the barrier film, or the metal film, the barrier film and In the polishing of the insulating film, it can hardly be used. Further, when silica of less than 20 m ² / g is used, the silica is liable to settle, and the stability of the abrasive is reduced, and there is a concern that scratches may increase.

When abrasive grains other than silica, for example, alumina are used as abrasive grains, in addition to the above-mentioned problems,
There is another problem that polishing scratches (scratch) often occur. When scratch occurs in the CMP polishing process,
Because the wiring of the device is disconnected or short-circuited,
This may cause a significant reduction in device yield.

As the silica used in the present invention, known silicas are used without any particular limitation as long as the specific surface area is satisfied. For example, fumed silica produced by burning silicon tetrachloride or silane-based gas in a flame, or sol-gel silica produced by hydrolysis using alkoxysilane as a raw material (hereinafter, also referred to as high-purity colloidal silica) And wet silica produced by using sodium silicate as a raw material and neutralized with a mineral acid, and colloidal silica produced by using the sodium silicate as a raw material by the Ostwald process. Among the above, high-purity colloidal silica is highly suitable because it has features such as high purity, and is unlikely to cause scratches due to spherical particle shape.

The concentration of the silica in the abrasive of the present invention is preferably in the range of 0.1 to 20% by weight. If the concentration of silica is less than 0.1% by weight, the polishing rate of the film to be polished may be reduced. If the concentration is more than 20% by weight, there is a problem in stability such as gelling of the abrasive. There are cases.

In the abrasive of the present invention, it is extremely important to use oxalic acid as the acid. That is, by using oxalic acid, the dissolution of the metal film when polishing reaches the barrier film can be effectively prevented while sufficiently maintaining the polishing rate of the metal film, and the metal film in the insulating film concave portion can be effectively prevented. Dishing can be prevented.

In the abrasive of the present invention, the concentration of the oxalic acid is preferably in the range of 0 to 1% by weight. In the abrasive of the present invention, in combination with the silica, the polishing rate of the metal film tends to greatly depend on the oxalic acid concentration in the abrasive. Therefore, when polishing the metal film, the oxalic acid concentration should be set higher, and when the polishing rate of the metal film should be reduced, the oxalic acid concentration should be set lower. In addition,
When the oxalic acid concentration exceeds 1% by weight, the polishing rate for the metal film becomes too high, so that the polishing control tends to be difficult.

In the present invention, the type of the oxidizing agent is not particularly limited, and a known oxidizing agent can be used. For example, peroxides, perchlorates, persulfates, oxidizable metal salts, oxidizable metal complexes and the like, among them, hydrogen peroxide and ammonium persulfate in terms of ease of handling, purity, etc. preferable.

In the abrasive of the present invention, the concentration of the oxidizing agent is preferably in the range of 0 to 10% by weight. In the polishing agent of the present invention, in combination with the silica, the polishing rate of the metal film tends to greatly depend on the oxidizing agent concentration in the polishing agent. Therefore, when polishing the metal film, the concentration of the oxidizing agent may be set higher, and when it is desired to reduce the polishing rate of the metal film, the concentration of the oxidizing agent may be set lower.

Incidentally, even if the concentration of the oxidizing agent exceeds 10% by weight, the effect of improving the polishing rate for the metal film is not often observed, and the use of the oxidizing agent having a high concentration is problematic in terms of danger. There is a concern that problems such as increased burden on wastewater treatment may occur.

In the use of the abrasive of the present invention, the order of addition of each component is not particularly limited, as long as all components are contained at the time of use, that is, at the time of polishing. However, in general, the oxidizing agent gradually decomposes when left in the air, and its oxidizing power often decreases. Therefore, it is desirable to add the oxidizing agent at the time of use.

When the metal film is polished using hydrogen peroxide as an oxidizing agent, the polishing agent of the present invention can be used for polishing a metal film at a hydrogen peroxide concentration of 0.2 to 6% by weight. Since the polishing rate is almost constant, a stable polishing rate can be obtained even if the oxidizing agent is slightly decomposed as described above, so that the polishing rate is very suitably used in terms of reproducibility and controllability of the polishing rate.

It is desirable that the silica in the polishing agent of the present invention is well dispersed in water, so that it is necessary to prepare the silica in advance, but oxalic acid and the oxidizing agent only need to coexist at least when polishing. Therefore, they may be mixed in a polishing apparatus or a pipe.

Therefore, with respect to oxalic acid and the oxidizing agent, it is possible to perform more advanced polishing by changing their concentrations within the above preferable range during the polishing process. For example, a relatively high concentration of oxalic acid and hydrogen peroxide are added in the initial stage to increase the polishing rate of the metal film, and in the final stage, the polishing rate is decreased by lowering the concentration of both or one of these additives. Such an embodiment is also feasible.

By doing so, the selectivity between the metal film and the barrier film or between the barrier film and the insulating film is adjusted to an optimum range, and the solubility (dishing) of the metal film on the wiring pattern or the electrode is further reduced. It is also possible.

According to the preferred polishing method, an insulating film having a concave portion for metal wiring is formed on the surface of a semiconductor substrate, and a metal film is formed thereon so as to fill the concave portion via a barrier film. When the metal film and the barrier film are removed by polishing to form a flattened surface between the insulating film and the metal film present in the recess, 0.1 to 20% by weight of silica and 0.1% of oxalic acid are used. To 1% by weight and an oxidizing agent of 0.1 to 10% by weight according to the present invention (hereinafter also referred to as a first abrasive)
The above metal film is polished by using (hereinafter referred to as first-stage polishing), and then 2 to 20% by weight of silica and 0% of oxalic acid are added.
The metal film and the barrier film are simultaneously polished using the polishing agent of the present invention (hereinafter, also referred to as a second polishing agent) containing 0.1 to 0.1% by weight and an oxidizing agent of 0 to 10% by weight (hereinafter, referred to as a second step). Polishing).

After the above polishing, silica is added in an amount of 0.1 to 20.
% By weight, substantially free of oxalic acid and oxidizing agent, p
The metal film, the barrier film, and the insulating film are simultaneously polished using the polishing agent of the present invention (hereinafter, also referred to as a third polishing agent) in the range of H5 to H9 (hereinafter, referred to as third-stage polishing). The above polishing method is also provided.

As described above, the polishing agent of the present invention can be used in the polishing step by changing the concentration of each component within the same component, that is, without changing the polishing agent component to other abrasive grains or acid. It is also possible to cope with any kind of polishing, whereby the polishing step can be performed continuously with one polishing apparatus while changing the concentration of each component. Further, in terms of wastewater treatment after polishing, wastewater from all steps can be treated with the same treatment equipment, which is industrially advantageous.

In the polishing method of the present invention, a typical example of the semiconductor substrate is a silicon substrate used for semiconductor devices such as ICs and LSIs, but the present invention can also be applied to semiconductor substrates such as germanium and compound semiconductors.

The insulating film is used for electrical isolation between wiring layers, and is not particularly limited as long as it is insulating. Silicon oxide film (plasma-TEOS film or S
OG film), an organic SOG film, and the like.

Further, the barrier film is a thin film formed between the insulating film and the metal film to prevent the diffusion of the wiring metal into the insulating film and to improve the adhesion of the metal film to the insulating film. In addition, a tantalum film, a tantalum nitride film, a titanium film, a titanium nitride film, a tungsten nitride film, and the like can be given. Among them, a tantalum nitride film is preferable.

Further, the metal film is a wiring material for forming a wiring pattern and an electrode, and examples thereof include an aluminum film, a copper film, and a tungsten film. Among them, the present invention is particularly effective for a copper film.

The polishing method of the present invention will be described in detail with reference to FIG.

The recess A provided in the insulating film formed on the surface of the semiconductor substrate is a groove or a connection hole formed on the insulating film for forming a wiring or the like.

First, (a) first-stage polishing is performed in which the barrier film 3 and the metal film 4 sequentially laminated on the insulating film 2 having the concave portion A are polished using (b) a first abrasive. By doing so, the metal film 4 is removed by polishing.

Next, (c) the barrier film and the metal film are simultaneously polished using the second abrasive, and if necessary, the metal film, the barrier film and the insulating film are used using the third abrasive. Are polished simultaneously.

In the first-stage polishing, the metal film can be removed while suppressing the occurrence of scratching and dishing by using oxalic acid as an acid and the abrasive of the present invention using specific silica. An extremely flat surface composed of a barrier film and a metal film can be formed.

Here, in the first stage polishing, it is desirable to polish the metal film efficiently at a relatively high polishing rate. Generally, the thickness of the metal film to be polished is 5000 to 20
Since the thickness is in the range of 2,000 Å, the polishing rate of the metal film is preferably 3,000 Å / min or more, and more preferably 5,000 Å / min or more.

Therefore, as the first abrasive, 0.1-20% by weight of silica, preferably 0.1-5% by weight,
Those containing 0.1 to 1% by weight of oxalic acid and 0.1 to 10% by weight of an oxidizing agent are suitably employed.

After removal of the metal film by the first-stage polishing, the surface to be polished includes the barrier film and the metal film buried in the concave portions in an exposed state.

Incidentally, the abrasive of the present invention can control the selectivity between the metal film and the barrier film by changing the silica concentration during the first stage polishing. That is, when the silica concentration of the first abrasive is less than 2% by weight, the above selectivity becomes 50 or more, and polishing using the barrier film as a stop layer is possible. When the silica concentration is 2% by weight or more, In this case, the selectivity becomes less than 50, and polishing can be continuously performed on the metal film and the barrier film.

In the second polishing step, it is necessary to remove the barrier film from the surface to be polished. In the second-stage polishing, there is an advantage that dishing hardly occurs when the barrier film is polished at a polishing rate equal to or higher than that of the metal film. Therefore, the selection ratio of the metal film to the barrier film (metal film / barrier film polishing rate ratio) is preferably 1.2 or less, and more preferably 1.

Since the thickness of the barrier film formed on the semiconductor substrate is generally in the range of 100 to 500 angstroms, the polishing rate of the barrier film in the second polishing is 100 to 1000 angstroms /. m
In the range of in, preferably in the range of 200 to 500 angstroms / min, it is easy to control, and the time required for removing the barrier film is preferably within 2 minutes, more preferably within 1 minute.

The polishing rate is 100 angstroms /
If the amount is less than 1000 min, the productivity may be reduced.
At Å / min or more, not only the barrier film, but also the underlying insulating film or metal film of the wiring may be polished too much, and it becomes difficult to stop polishing at a desired position, resulting in poor controllability. There is.

In order to satisfy the above requirements, as a second abrasive, silica is 2 to 20% by weight, preferably more than 5% by weight and not more than 10% by weight, oxalic acid is 0 to 0.1% by weight,
It is desirable to use one containing 0 to 10% by weight of an oxidizing agent. When the concentration of oxalic acid exceeds 0% by weight within the above range, the concentration of the oxidizing agent is preferably 0 to 0.2% by weight. In particular, the use of oxalic acid at 0% by weight and the oxidizing agent at 0% by weight means that when the composition is subsequently changed to the third polishing agent used in the third-stage polishing, only the silica concentration is adjusted. This is preferable because the above change can be easily made.

As described above, the polishing rate of the metal film of the present invention tends to largely depend on the concentration of oxalic acid and the oxidizing agent among the above-mentioned constituents. In order to obtain it, the concentrations of oxalic acid and oxidizing agent may be adjusted to the above ranges. In the polishing agent of the present invention, the polishing rate of the barrier film tends to depend on the silica concentration. Therefore, in order to obtain a desired polishing rate, the silica concentration may be adjusted to the above range. By doing so, the selection ratio of the barrier film to the metal film can be adjusted to a desired value.

Further, since the second abrasive has a lower concentration of oxalic acid than the first abrasive, dishing of the metal film buried in the concave portion is more unlikely to occur. .

In the present invention, in order to obtain a more highly planarized semiconductor substrate surface, a metal film,
Third-stage polishing for polishing three types of films, that is, a barrier film and an insulating film, at substantially the same polishing rate can be performed.
It is preferable that the third polishing agent used for such polishing can polish the metal film, the barrier film, and the insulating film at substantially the same polishing rate. Particularly preferably, the selectivity (barrier film / metal film polishing rate ratio and insulating film / metal film polishing rate ratio) of the metal film to the barrier film and the metal film to the insulating film is preferably 0.2 to 5, and more preferably 0.2 to 5. Preferably it is 0.5-2, especially 0.8-1.2.

The polishing rate of the above-mentioned third polishing agent is as follows.
The barrier film and the insulating film each have a range of 30 to 500 Å / min, preferably 50 to 30 Å.
0 angstrom / min. If the polishing rate exceeds 500 angstroms / min, the insulating film may be polished too much and controllability may be poor. If it is less than 30 angstroms / min, it may take too much time.

In order to satisfy the above requirements, silica is added in an amount of 0.
A third abrasive containing 1 to 20% by weight, preferably 0.1 to 5% by weight, substantially free of oxalic acid and an oxidizing agent and having a pH in the range of 5 to 9 can be suitably used.

In the polishing agent of the present invention, the polishing rate of the metal film greatly depends on the concentrations of oxalic acid and the oxidizing agent. . Further, the polishing rate of the metal film, the barrier film, and the insulating film can be adjusted by adjusting the concentration of silica.

The pH of the third abrasive is 5-9.
, Preferably in the range of 6 to 8, the metal film is hardly corroded, which is preferable. When the pH is in the above range, the metal film, the barrier film, and the insulating film tend to be polished at almost the same polishing rate, which is preferable. If the pH of the polishing agent is less than 5, the polishing rate of the metal film may exceed 9, and the polishing rate of the insulating film may be significantly higher than the polishing rate of the barrier film. In such a case, dishing easily occurs in the metal film or the insulating film,
The flatness of the surface of the semiconductor substrate may be reduced.

Each of the above three polishing steps (1.
Polishing of metal film. 2. Simultaneous polishing of metal film and barrier film.
3. In the simultaneous polishing of the metal film, the barrier film, and the insulating film), the following methods can be used to adjust the concentration of each component of the polishing agent of the present invention and control the polishing time. One is to measure the time required for each process in advance,
This is a method in which the concentration of each component of the abrasive is changed every time of each step. When the same semiconductor substrate is repeatedly polished, the above-described method can be sufficiently controlled. Another method is to use an endpoint detector utilizing various principles. Many types of end point detectors are commercially available, such as a type that detects a change in torque (power) of a surface plate of a polishing machine and a type that optically detects the surface state of a substrate to be polished. A sequence can also be arranged to change the concentration of the constituents of the abrasive using the signal detected by the endpoint detector.

In order to adjust the concentration of each component of the polishing agent, three types of polishing agents whose concentrations of the respective components have been adjusted are prepared from the beginning, and are switched and used in each step. Alternatively, a solution may be prepared for each component, and may be mixed and used at a desired mixing ratio in a polishing apparatus or a pipe in each step.

[0058]

As will be understood from the above description, according to the polishing agent of the present invention, the selectivity in polishing a metal film, a barrier film and an insulating film can be arbitrarily changed. It is a polishing agent that can simultaneously polish a film and a barrier film, and can polish a metal film, a barrier film, and an insulating film at substantially the same polishing rate.

Therefore, the polishing step and the wastewater treatment step after polishing can be simplified, and the industrial contribution is extremely large.

The first abrasive of the present invention is characterized in that a metal film can be polished at a high polishing rate of 3000 angstroms / min or more, and that the metal film has low solubility in the metal film.

[0061]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

(Polishing test) Copper (Cu) film as a metal film,
A polishing test was performed using a 4-inch silicon wafer having a tantalum nitride (TaN) film as a barrier film and a silicon oxide (SiO ² ) film formed on the surface as an insulating film. The polishing pad is IC1000 / SUB manufactured by Rodale Nitta
Using A400, a polishing test was performed under the conditions of a processing pressure of 300 g / cm ² , a platen rotation speed of 40 rpm, and an abrasive dropping speed of 80 ml / min, to obtain a polishing rate.

Examples 1 to 24 and Comparative Examples 1 to 6 Various kinds of silica, acid and hydrogen peroxide solution shown in Table 1 were mixed with water so as to have the concentrations shown in Table 1, and abrasives were respectively adjusted. A polishing test was performed.

The colloidal silica shown in Table 1 had a purity analysis which showed that all of the impurity metal elements such as Na, K, Al, Fe, and Cr were 0.1 ppm or less, and that the average particle diameter was about It was a highly monodisperse spherical silica particle of 90 nm and about 40 nm. An abrasive using alumina instead of the above silica was also tested.

Table 2 shows the polishing rates of the various films and the selectivity calculated from the polishing rates as a result of the polishing test.

When the surface of the polished wafer was observed using a condensing lamp, the wafer polished with the abrasive containing alumina was more polished than the wafer polished with the abrasive containing silica.
It was confirmed that many scratches were generated on the surface.

[0067] From the above results, the first as the abrasive grains of the abrasive specific surface area 20 m ² / g or more, is effective silica in the range of less than 80 m ² / g, thereby, possible to polish the metal film at a high speed 200 Å / mi barrier film
It was found to be excellent in that it can be polished at a suitable polishing rate of n or more. In the first abrasive, when the silica concentration was 2% by weight or less, the Cu / TaN ratio was 50 or more, and it was found that the selective polishing of the metal film was excellent.

For efficient polishing of the Cu film, the silica concentration should be 0.1% by weight or more, the oxalic acid concentration should be 0.1% by weight or more, and the oxidizing agent concentration should be 0.1% by weight or more. Turned out to be desirable.

In the second polishing agent, it was found that the polishing rate of the TaN film could be at least 100 Å / min when silica having a specific surface area of 20 m ² / g or more and less than 80 m ² / g was used.

It was also found that the Cu film could be polished at a polishing rate of 5000 Å / min or more even when ammonium persulfate was used instead of hydrogen peroxide as the oxidizing agent.

The experiments by the present inventors have confirmed that the dissolution rate of the Cu film greatly depends on the type of acid in the polishing slurry of the present invention. In the experiment, only the dissolution rate by an acid was measured, and as a result, 361 Å / min of nitric acid, 378 Å / min of hydrochloric acid,
Sulfuric acid 441 angstroms / min, acetic acid 500 angstroms / min or more, oxalic acid 14 angstroms / min, succinic acid 71 angstroms / mi
n, citric acid was 227 Å / min, and malonic acid was 284 Å / min. The results show that oxalic acid has a remarkably low dissolution rate. For reference, when a similar test was performed in pure water (pH 7), the dissolution rate of the Cu film was about 2 Å / min.

From the above, it was confirmed that when oxalic acid was used as a kind of acid, polishing in which dishing hardly occurred was possible.

[0073]

[Table 1]

[0074]

[Table 2]

Example 25 A silicon wafer having a width of 10 was formed on an SiO ₂ film formed on the surface of a silicon wafer.
Using a TEG wafer in which 0 μm wiring grooves are formed at intervals of 100 μm and a TaN film having a thickness of about 200 Å and a Cu film having a thickness of about 1.5 μm are sequentially stacked thereon, the silicon wafer surface is formed. First, polishing was performed for 150 seconds with the abrasive of Example 1. As a result, the Cu film above the surface of the TaN film was removed, and the TaN film and the Cu film in the wiring trench were exposed. Subsequently, when polishing was performed for 30 seconds with the polishing agent of Example 16, the TaN film was removed, and the SiO ₂ film in portions other than the wiring grooves and the Cu film in the wiring grooves were exposed. Further, using the abrasive of Example 23, 2
Polished for 0 seconds.

[0076] When a silicon wafer surface after polishing was observed by an electron microscope, scratches and dishing was not observed at all, the SiO ₂ film and the wiring groove in the portion other than the wiring grooves Cu
There was almost no step on the surface of the film, and it was confirmed that a flat surface was formed.

From the above results, it was found that the polishing rate of the metal film, the barrier film and the insulating film can be arbitrarily adjusted by adjusting the concentrations of the oxalic acid, the oxidizing agent and the silica as the constituents. It was confirmed that it could be changed to

Also, by merely changing the concentration of the above constituent components, polishing of a metal film (first-stage polishing), polishing of a metal film and a barrier film (second-stage polishing), and furthermore, metal film, barrier film and insulating film It can be seen that productivity can be extremely high because the polishing (third stage polishing) can be continuously performed. Furthermore, it has been found that an extremely flat semiconductor substrate surface can be formed by employing the polishing agent of the present invention and the polishing method of the present invention using the same.

Comparative Example 7 Polishing was carried out in the same manner as in Example 25 except that hydrochloric acid was used instead of oxalic acid (adjusted to pH 2.0) in the first stage polishing. As a result, SEM observation revealed that S
Dishing was confirmed on the surface of the metal film existing in the wiring groove of the iO ₂ film.

The same polishing was carried out by replacing the above acid with succinic acid, citric acid and malonic acid. As a result of observation by SEM, similar dishing was observed on the surface of the metal film existing in the wiring groove of the SiO ₂ film. Was confirmed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a general polishing method.

FIG. 2 is a schematic view showing a typical embodiment of the polishing method of the present invention.

[Explanation of Symbols] A recess 1 semiconductor substrate 2 insulating film 3 barrier film 4 metal film

Claims (3)

[Claims] A specific surface area measured by a BET method is 2
0.1 to ² m ² / g or more and less than 80 m ² / g of silica.
0% by weight, 0 to 1% by weight of oxalic acid, 0 to 10% of oxidizing agent
Abrasives characterized by containing water by weight, with the balance being water. 2. An insulating film having a concave portion for metal wiring is formed on the surface of a semiconductor substrate, and a metal film is formed thereon so as to fill the concave portion via a barrier film, and then the metal film and the barrier film are polished. To form a flattened surface between the insulating film and the metal film present in the recesses, by using 0.1 to 20% by weight of silica, 0.1 to 1% by weight of oxalic acid, and an oxidizing agent. The metal film is polished using the polishing slurry according to claim 1 containing 0.1 to 10% by weight of silica.
A polishing method comprising simultaneously polishing a metal film and a barrier film by using the polishing agent according to claim 1, comprising 20% by weight, 0 to 0.1% by weight of oxalic acid and 0 to 10% by weight of an oxidizing agent. . 3. The polishing method according to claim 1, wherein the polishing method according to claim 2 includes 0.1 to 20% by weight of silica and is substantially free of oxalic acid and an oxidizing agent and has a pH of 5 to 9. A polishing method comprising simultaneously polishing a metal film, a barrier film, and an insulating film using an abrasive.